1. Field of the Invention
The present invention relates to an improved dampening system for elevators and similar devices. More specifically, the present inanition relates to a safety feature that prevents rapid descent of an elevator or similar device.
2. Prior Art
Elevators, trams and other devices for transporting items and people up and down steep slopes and vertically through buildings have been in use for over a century. There has always been a danger that, should the device fail, the elevator car or tram would fall a great distance resulting in damage to goods and death to passengers. Several devices have been designed to operate as brakes to stop a rapidly descending car or tram upon failure of the elevator device.
U.S. Pat. No. 105,177 issued to Copeland on Jul. 12, 1870 discloses in addition to the ordinary brake, a water or other fluid cylinder furnished with a passage connecting the two ends, in such a manner that a valve in the connecting-passage regulates the rapidity with which a piston may be worked by the obstruction it offers to the passage of the water or other fluid, so that the adjustment of the valve regulates the speed of the piston, and fixes the limit at which the car may be permitted to run down the incline. It does not disclose the use of a hydraulic motor safety device attached to the car.
U.S. Pat. No. 205,537 issued to Garrison on Jul. 2, 1878 discloses a safety brake for cars, being more particularly adapted for use on inclines in mines, and which are lowered and raised by means of a wire cable or rope attached to an engine on the surface (typical emergency brake system). This device simply applies frictional force to one of the rails upon which the car rides.
U.S. Pat. No. 236,184 issued to Schmidt on Jan. 4, 1881 discloses a pneumatic braking system. An air powered braking system halts descent of an elevator once a certain speed is reached.
U.S. Pat. No. 527,894 issued to Smith on Oct. 23, 1894 discloses a safety appliance for use in connection with cars upon inclined railways, and it has a stationary or fixed cable in connection with the railway, so arranged with reference to the car upon the track as to permit the gripping of the cable by the gripping mechanism upon the car. This invention provides a safety device that immediately stops the car and does not allow for a slow descent.
U.S. Pat. No. 3,415,343 issued to Svensson on Dec. 10, 1968 discloses a catch apparatus for the elevator cages of scaffold elevators and other similar elevators, on which the elevator cage by means of a driven gear wheel climbs along a toothed rack in a mast structure for the elevator.
U.S. Pat. No. 3,924,710 issued to Shohet on Dec. 9, 1975 discloses a hoist with a rack and pinion drive assembly for raising and lowering the lift frame of the hoist and a rack and pinion overspeed mechanism for braking the lift frame when the hoist exceeds a predetermined speed.
U.S. Pat. No. 3,967,703 issued to Martin on Jul. 6, 1976 discloses a rack-and-pinon type hoist with an improved braking apparatus that includes a spring buffer, preferably hydraulic, carried by the cage of the hoist, a rotatable shaft also carried by the cage and positively engaged with a member extending along the mast so as to be driven in rotation by movement of the cage along the mast and connecting means for engaging the shaft and the buffer comprising a centrifugal governor driven by rotation of the shaft and operating, in response to rotation of the shaft in excess of a predetermined rate of rotation, to provide positive drive to a linearly movable member, the movement of which is opposed by the buffer.
U.S. Pat. No. 4,046,226 issued to Flinchbaugh on Sep. 6, 1977 discloses an elevator platform that rides on parallel tracks which may be adapted for vertical or inclined conveyance. Each track is slotted along its length, through which slot the platform extends and is connected to a trolley driven by a continuous chain. Each track is tubular and generally rectangular, and each encloses another tubular, rectangular member which provides a space for the chain return and electrical conduits, and which provides support for the trolley. Each trolley has an upper pair of rollers bearing against the inside of the hollow track straddling the slot, and lower rollers bearing against the top surface of the inner tubular member. Interrupt and safety precautions are provided based on chain breakage, excessive speed, overload, or contact with foreign objects in the path of the elevator platform. The safety precautions provide for an immediate stop
The designs of the prior art designed to detect when an elevator car accelerates passed a predetermined speed. The device then rapidly stops the elevator car. This sudden stops jerks what ever is in the car and can cause damage to products and injure passengers. In addition, the car may be stopped at an inconvenient spot. An elevator may be caught between floors and a tram may be stopped only halfway down its track and difficult to get to. None of the prior art discloses means for slowing down rather than stopping an elevator car. Neither do they provide means for an elevator whose power has failed to safely fall to the bottom of its track.
It is therefore desirable to provide an elevator dampening system that does not suddenly stop an elevator car thus jarring its contents.
It is also desirable to provide a dampening system that allows an elevator car to slowly return to the bottom of a shaft or track.